Losing face: what cows, dogs, and Neanderthals can tell you about why you have wisdom teeth

The story of wisdom teeth is as interesting as wisdom teeth are unpleasant.

One of the characteristics of the modern human skull is that the face is located primarily under the eyes. What the hell does that mean? For comparison, let’s look at some not-terribly-exotic animals. We’ll start with a nice side view of a cow.

Check out the cow’s muzzle. Is there any sense in which you could say that the cow’s face is under its eyes? No–the muzzle protrudes out frontally quite a bit.

In fact, by definition, a muzzle (or snout) protrudes. From the Wikipedia post on the subject: “A snout is the protruding portion of an animal’s face, consisting of its nose, mouth, and jaw. In many animals the equivalent structure is called a muzzle, rostrum or proboscis.”

There’s quite a bit of variety in muzzle (snout) shapes in the animal kingdom. Here are some possibilities in dogs. Mouse-over the pictures for technical terms that describe these different skull shapes.

If we look at various and sundry apes, we see that they have protruding muzzles (or snouts), as well. (Scroll down past the pictures.) Compare the human, the chimp, the orangutan, and the macaque, and you’ll note that the three non-humans have protruding muzzles. The human: no. (BTW: I don’t think that the macaque is an ape.)

We can see how this anatomy relates to the rest of the skull if we look at the skull from the underside. Let’s go back to dogs–or dog-like things, at any rate. Here are four different canid species. Look at the second row from the top–that’s the underside of the skull. The narrow thing sticking out towards the front of the skull is the palate, or roof of the mouth. That’s the bone of the muzzle.

Where this becomes relevant to humans is that over the course of human evolution, we’ve gone from having protruding snouts to not having them. It’s hard to find a single picture that illustrates the progression, so I’ll run some individual ones by you. Here’s an Australopithcus africanus. Australopithecus was around from about 4 million years ago to about 2 million years ago. They’re probably ancestral to us–if not, we share a common ancestor. Note the prominent protrusion.

Here’s a nice side-by-side of a Homo erectus skull and a modern human skull.

Homo erectus was around from about 1.9 million years ago until about 70,000 years ago. It’s probably an ancestral species to modern humans. The frontal protrusion is nothing like the australopithecine one, but it’s still there. (Keep scrolling down–alignment problems…)

Neanderthals were around from maybe 250,000 years ago until about 40,000 years ago. I’m not clear on the arguments as to whether or not they’re ancestral to modern humans, but we probably inbred with them. Not much protrusion left, at this point.

So, how does this relate to the question of why you have wisdom teeth? The thought is that as the muzzle of early hominids shortened down to what we (don’t) have today, it resulted in a crowding of the teeth into a smaller anterior-posterior (front to back) area.

Do we get anything out of all of this change in oral anatomy? Actually, modern humans do have a fairly unique oral cavity morphology (shape, in this sense of the word morphology). One of the results of that morphology is a lot more space in which to make different kinds of sounds, and those possibilities do indeed get exploited in the languages of the world. More on that another time. Until then, here’s some relevant French vocabulary.

le museau: muzzle, snout

le groin: pig snout

le boutoir: wild boar snout

la dent de sagesse: wisdom tooth

By the way: if you’re interested in this kind of thing, it’s worth checking out both the English-language Wikipedia page on wisdom teeth and the French-language Wikipedia page on wisdom teeth. Each one has interesting content that the other one doesn’t.

4 thoughts on “Losing face: what cows, dogs, and Neanderthals can tell you about why you have wisdom teeth”

Wisdom teeth can be a pain. Removing one eons ago I remember as if it were yesterday. A friend is due for one out in the next few days and is having kittens. Good thing we’re presumably over with the toughest part of our evolutionary process. Or are we?

We are not! There’s a genetic component to whether or not you have wisdom teeth. Wikipedia says that it’s related to a gene called PAX9, and maybe others. It’s pretty unusual for traits to be controlled by just one gene. I took a quick look at the Online Mendelian Inheritance in Man database and found a number of genes that could be involved, although that doesn’t necessarily mean that they are. Probably good candidates, though. If you want to know more: http://www.ncbi.nlm.nih.gov/omim/?term=wisdom+tooth